A modelling analysis is performed on JET D and DT discharges, where W dust influx across the separatrix, in the pedestal edge region may affect L-H-L mode transition. The experimental basis of the proposed approach stems from the observation that transient impurity events (TIEs) are often associated with the presence of a shower of particles seen in the camera images and with strong optical emission. If the localised source of radiation is a number of heated or ablated large dust particles, then the questions addressed here are: how far will the ablated dust material penetrate and what effect will this have on the edge of the pedestal in relevant JET D and in a high fusion yield D-T discharges. The methodology is based on the use of an upgraded version of the ballistic code DUSTTRACK and a new code PELLYTIX for dust ablation modelling. Considering a reasonable amount of dust released from the tiles, the analysis shows that the ablation-penetration depth is visible in the density profiles modification, but not disastrous for tokamak operation in high regimes.

Empirical studies of dust-surface collisions for metal and carbon projectiles impacting on metal targets in the velocity range from a few m/s to those in excess of 1 km/s have been carried out with the use of a modified pellet injection system. The selected projectile/target shapes, sizes and materials are mimicking the scenario of dust colliding with plasma facing components (PFCs) of a metal machine. The low velocities (10's m/s) reported here, characteristic for dust motion in tokamak scrape-off layer plasmas, are in the range of sticking phenomenon; the critical velocity and size for bouncing off are essential and timely inputs for the dust dynamics codes and statistical models aiming to predict dust transport and redeposition on PFCs. © 2013 Elsevier B.V. All rights reserved.